(i) Al reacts with conc.`HNO_(3)` to form a very thin film of aluminium oxide on its surface which protects it from further action.
`2Al (s) + 6 HNO_(3) (conc.) rarr underset("Alumina")(Al_(2)O_(3)(s)) + 6NO_(2) (g) + 3H_(2)O (l)`
thus, Al becomes passive and hence aluminium containers can be used to transport conc. `HNO_(3)` .
(ii) `NaOH` reacts with Al to evolve dihydrogen gas. The pressure of the gas thus produced can be used to open clogged drains .
`2Al(s) + 2NaOH (aq) + 2H_(2)O(l) rarr 2NaAlO_(2) (aq) + 3H_(2)(g)`
(iii) Graphite has layered structure in which the different layers are held together by weak can der Waaks forces and hence can be made to slip over one another. Therefore, graphite acts as a lubricant.
(iv) Diamond is very hard and hence can be used as an abrassive.
(v) Aluminium alloys such as duralumin is light, tough and resistant to corrosion and hence is used to make aircraft body.
(vi) Al reacts with `H_(2)O` and dissolved `O_(2)` to form a thi film of alumionium oxide.
`2Al (s) + O_(2) (g) + H_(2)O (l) rarr Al_(2)O_(3) (s) + H_(2) (g)`
A very very small amount of `Al_(2)O_(3)` may dissolve to give a few ppm of `Al^(3+)` ions in the solution. Since `Al^(3+)` ions are injurious to health, therefore, drinking water should not be kept in aluminium utensile overnight.
(vii) On weight to weight basis, aluminium conducts twice as Cu. Therefore, it is used in trasmission cables.
